The spring pests to look for in alfalfa are alfalfa weevil, clover leaf weevil and potato leaf hopper.

While weevils overwinter as eggs and adults and can infest alfalfa and damage the first cutting in the spring, the potato leaf hopper migrates in and damages the second and third cuttings.

There are other insects that feed on alfalfa such as meadow spittlebug, tarnished plant bug, alfalfa plant bug, alfalfa blotch leaf miner, pea aphid and grasshoppers, but they are often minor.

The one to watch out for this spring is the alfalfa weevil. The alfalfa weevil spends the winter as an adult in the crowns of the alfalfa plant or under leaves or other debris. Adults emerge when air temperatures reach 60 F, feed on alfalfa leaflets and lay eggs in the feeding cavities which hatch about 2 weeks later.

Newly emerged larva feed in the cavity, then move to leaf buds and lastly leaflets and continue to feed. Most feeding occurs before the first cutting and the first harvest eliminates the pressure. Many larvae are destroyed by the cutting process the remainder are left exposed to predators, high temperatures, direct sunlight and lack of food and die off.

However a heavy spring infestation and reduce yield and quality of alfalfa so you can scout, see if you are at the economic threshold and then spray. The threshold for treatment is 25% to 50% of leaflets are skeletonized (areas between the veins eaten out) and there are three or more larvae per stem.

If early harvest is possible, it is the control method of choice. If an insecticide application is chosen, do not apply during bloom. Scout for larvae and determine the threshold before spraying. And check with your retailer for an insecticide and rate.